小编Sah*_*ati的帖子

有谁知道如何使我的十字准线透明或不透明？

我正在尝试制作一个看起来像这样的十字准线：

这是代码：

import sys
from PyQt5 import QtCore, QtGui, QtWidgets

class Crosshair(QtWidgets.QWidget):
    def __init__(self, parent=None, windowSize=24, penWidth=2):
        QtWidgets.QWidget.__init__(self, parent)
        self.ws = windowSize
        self.resize(windowSize+1, windowSize+1)
        self.pen = QtGui.QPen(QtGui.QColor(0,255,0,255))
        self.pen.setWidth(penWidth)
        self.setWindowFlags(QtCore.Qt.FramelessWindowHint | QtCore.Qt.WindowStaysOnTopHint | QtCore.Qt.WindowTransparentForInput)
        self.setAttribute(QtCore.Qt.WA_TranslucentBackground, True)
        self.move(QtWidgets.QApplication.desktop().screen().rect().center() - self.rect().center() + QtCore.QPoint(1,1))


    def paintEvent(self, event):
        ws = self.ws
        d = 241
        painter = QtGui.QPainter(self)
        painter.setPen(self.pen)
        # painter.drawLine( x1,y1, x2,y2    )
        painter.drawLine(ws/2, 0,               ws/2, ws/2 - ws/d)   # Top
        painter.drawLine(ws/2, ws/2 + ws/d,     ws/2, ws)   # Bottom
        painter.drawLine(0, ws/2,               ws/2 - ws/d, …

我有一个名为 (First) 的功能组件

function First() {
    const [count,setCount]=useState(0)

    console.log("component first rendering") // this logging is happening twice


    return (
        <div>
            first component
        </div>
    )
}

当我最初运行应用程序时，console语句记录了两次，为什么它应该只记录一次，因为我没有明确更新状态。